Improvement in apparatus for evaporating tannic extracts



l'H. Mckenzle.

-Apparatus for Evaporatin'g Tannic Extracts. l v10.150,596. Patented May 5, 1874.

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of, and formed by short pieces f, placed between and joining the edges of the plates and within their circumference. Any desired number ot these oblique lines of short pieces can be laid within the circumference of the screw, their function being to eiicct a thorough commingling of the light and heavy liquors, and at the same time create a movement thereof counter to that produced by the screw-plates; for it will be seen that as the two screws occupy the relation to each other of a diameter and a surface oblique position they must necessarily produce opposite ei'ects upon the liquor from one and the saine motion of the compound screw.

As the construction of the screw of other material than wood is too expensive, and as wood blades of single thickness are liable to warp and break apart under the combined action of heat and moisture, I therefore overcome these serious objections by constructing the screw-blades of two thicknesses, each being composed of several sections, g, the divisional lines h ot' the sections of each thickness being approximately at right angles. 'Ihese two thicknesses are simultaneously built up and riveted together on the shaft, forming a solid screw-blade of great strength and rigidity, and dispensing entirely with all bracing devices hitherto iound necessary even in the construction of plain disks.

The state of the art shows that screw-evapora-tors are not new, and that in connection with such both hot air and steam have been used conjointly; but in no instance am I aware that a compound wood-screw has been used to obtain the advantages stated, or that hot air has been employed to first generate and then absorb and carry away aqueous vapors.

I claiml. In an evaporator, the heating-pipes a, in combination with the side-perforated pipes d, connected, as described, with the inlet-pipe c, whereby a current of heated air first generates and then absorbs, and carries away aqueous vapors from the body of the liquor, substantially as described. e

2. The pipes d d, having their perforations e ran gin g obliquely upward toward the central circumference of the screw, to project the air around and upon the screw-blades, in the manner and for the purpose described.

3. A compound screw for iluid-evaporators, consisting of a diameter and an oblique surface-screw, to operate as described.

4. rIhe blades of an evaporating-screw constructed of two thicknesses of separate and distinct sections, g, the divisional lines h ot each thickness being laid approximately at right angles, as and for the purpose described.

5. A screw evaporator having a surfacescrew formed of short pieces f, advancing in echelons between and within the main screw, substantially as described.

In testimony that I claim the foregoing as my own, I have affixed my signature in presence of two witnesses.

HENRY MCKENZIE.

Witnesses A. E. H. J oI-INsoN, J. W. HAMILTON J onNsoN. 

